Abstract-Longitudinal Component Properties of Circularly Polarized Terahertz Vortex Beams

 

Miao Wang, Xinke Wang, Peng Han, Wenfeng Sun, Shengfei Feng, Jiasheng Ye, Yan Zhang

https://www.frontiersin.org/articles/10.3389/fphy.2021.736831/full

A circularly polarized vortex beam possesses similar focusing properties as a radially polarized beam. This type of beam is highly valuable for developing optical manufacturing technology, microscopy, and particle manipulation. In this work, a left-hand circularly polarized terahertz (THz) vortex beam (CPTVB) is generated by utilizing a THz quarter wave plate and a spiral phase plate. Focusing properties of its longitudinal component Ez are detailedly discussed on the simulation and experiment. With reducing the F-number of the THz beam and comparing with a transverse component Ex of a general circularly polarized THz beam, the simulation results show that the focal spot size and intensity of its Ez component can reach 87 and 50% of Ex under a same focusing condition. In addition, the experimental results still demonstrate that the left-hand CPTVB can always maintain fine Ez focusing properties in a broad bandwidth, which manifest the feasibility of this class of THz beams.

Abstract-The effect of infrared plasmon on the performance of Si-based THz detectors

He Zhu, Jintao Xu, Jiaqi Zhu, Miao Wang, Huizhen Wu, Ning Li, Ning Dai

http://link.springer.com/article/10.1007/s10854-016-5598-7

Plasmons in metals have great impact on light emission, propagation, and detection in visible and infrared light wave frequencies. To explore plasmonic effect on the THz detection, both a backside-illuminated and a topside-illuminated blocking impurity band (BIB) THz detectors are developed and significant influence of plasmonic effect on the performance of BIB THz detectors is observed. The plasmonic effect in the heavily doped semiconductor layer of BIB THz detectors causes high reflectance of THz radiation which curtails the detection frequencies of the backside-illuminated BIB detectors. However, due to the advantages of flip-chip package and high quantum efficiency, the dark current, the responsivity, and the detectivity of the backside-illuminated detector shows superior characteristics to the topside-illuminated detector. The performance of the THz detector could be further improved with the suppression of the plasmonic effect.